Regulated power supplies typically supply voltage and current to electrical systems, such as microelectronic devices. The regulated power supply delivers power from a primary source to an electrical load at the specified current, voltage, and power efficiency. Many systems use switching power converters (SPCs) due to their high efficiency, high current capability, and topology flexibility. In addition, SPCs can be designed to provide the very precise voltage and current characteristics required by devices such as microprocessors, microcontrollers, memory devices, and the like.
Power requirements for various applications, such as emerging leading edge technology microprocessors, have become very difficult to satisfy. As the speed and integration of microprocessors increases, the demands on the power regulation system increase. In particular, as gate counts increase, the power regulation current demand increases, the operating voltage decreases, and transient events (e.g., relatively large voltage spikes or droops at the load) typically increase in both magnitude and frequency. Some emerging microprocessors are expected to run on less than 1.3 volts and more than 100 amperes.
SPC's utilizing step-down multi-phase buck converters have been the preferred topology to meet the low voltage and high current requirements of microprocessors. With the advent of increasingly complex power regulation topologies, digital techniques for power converter control, specifically in multiphase designs, can improve precision and reduce the system's total parts count while also supporting multiple applications in the same power system through digitally programmable feedback control.
Existing feedback controls have taken voltage measurements from the load, as well as from the individual output phases. The feedback information has been used to adjust the width of the pulses produced by each of the phases of a multi-phase buck regulator system to bring the supplied voltage and current within the load line tolerances specified by the microprocessor manufacturer. Active Transient Response (ATR) has been used for high frequency response to rapidly changing power requirements at the load by quickly activating multiple phases to supply or drain (as the case requires) more current to or from the load, thereby temporarily overriding the generally slower overall voltage regulator system response.
The measurement of load current is important for meeting microprocessor power requirements that specify a load line and active voltage positioning by defining narrow parameters within which current must be supplied at a specified voltage. In addition, leading edge microprocessors may specify current levels that must not be exceeded to avoid damage. To measure current, conventional systems use trimmed current sense circuitry and tight component tolerance to enhance accuracy. The solution offers limited accuracy, however, because the inherent errors accumulate over multiple sources and are not completely accounted for.